1. Field of the Invention
The present invention relates to equipment for separating liquids from associated gases in liquid-gas mixtures. More particularly, the present invention is directed to separation of molten sulfur from process streams having sulfur and gas mixtures, such as oil refineries.
2. Description of the Related Art
Many industrial operations require separation of liquids from associated gases in two-phase mixtures. For example, gaseous compounds containing sulfur, such as hydrogen sulfide, mercaptans, carbonyl sulfide, and carbon disulfide, exist in natural gas. Such gaseous compounds are produced as by-products in petroleum refining operations. Because sulfur has many useful applications and can most easily be transported in molten form, it is often necessary to separate the molten liquid sulfur from associated gases.
In industrial applications, gas streams containing sulfur compounds are processed to remove sulfur (primarily in the form of hydrogen sulfide). The gas streams are then further processed to form liquid sulfur in sulfur recovery units.
Conventional sulfur recovery units include a seal leg or trapping device to separate molten sulfur from the gas stream. The molten sulfur is condensed from the remaining gas stream.
Sulfur traps associated with sulfur recovery units, as historically practiced, include two concentrically arranged vertical pipes. The vertical pipes may extend approximately twenty feet to twenty-five feet into the ground. Process stream was introduced into the inner pipe, and molten sulfur was discharged from the outer pipe. The annular arrangement of the inner pipe and outer pipe provided a sulfur trap preventing tail gases from being discharged with the molten sulfur.
U.S. Pat. No. 5,498,270 to the present inventor discloses a sulfur trap that includes a spherical float in an upper chamber, a cylinder having a horizontal opening to a lower sulfur discharge chamber, and guides. The float is disengaged from the cylinder when floating in liquid sulfur and seals the cylinder opening at low levels of liquid sulfur.
U.S. Pat. No. 7,112,308 to the present inventor discloses a sealing device for a sulfur trap with a float, together with a counterweight and a cleaning rod to reduce solid sulfur buildup.
A jacket is commonly provided outside conventional sulfur traps, with steam circulated between the jacket and the outer sulfur trap surfaces to maintain the temperature of the sulfur trap at a level to maintain the sulfur in a liquid phase.